1. Field of the Invention
The present invention relates to patient interface devices for transporting a gas to and/or from an airway of a user, and in particular, to a patient interface device including a dynamic self adjustment mechanism for adjusting, for example and without limitation, mask position and/or pressure.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure.
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including a mask component on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal cushion having nasal prongs that are received within the patient's nares, a nasal/oral mask that covers the nose and mouth, or a full face mask that covers the patient's face. The patient interface device interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head.
For such patient interface devices, a key engineering challenge is to balance patient comfort against mask stability, i.e., the patient interface device stays properly fitted on the user. This is particularly true in the case of treatment of OSA, where such patient interface devices are typically worn for an extended period of time. As a patient changes sleeping positions through the course of the night, masks tend to become dislodged, and the seal can be broken. A dislodged mask can be stabilized by increasing strapping force, but increased strapping force tends to reduce patient comfort. This design conflict is further complicated by the widely varying facial geometries that a given mask design needs to accommodate.
One area where facial geometries vary a great deal is the angle of the base of the nose (known as the nasolabial angle). As is known, this angle can range from ˜58° to ˜114° (Ave±1SD). This creates difficulty in providing a single patient interface design that fits a range of users. Another area where fit and comfort is often a concern is the bridge of the patient's nose, as many patient interface devices will apply a pressure to this area. If this pressure is not able to be managed effectively, either or both of a poor fit or patient discomfort will result, thereby limiting the effectiveness of the device.